There are mainly two well-known types of systems for directional drilling of wells: 1) push-the-bit system; and 2) point-the-bit system. The push-the-bit system controls the well drilling direction by pushing the sidewall of the well at the opposite side against the designated drilling direction, as described in the U.S. Pat. No. 6,206,108 issued to MacDonald et al on Mar. 27, 2001. The point-the-bit system directly points the drill bit at the planned drilling direction, as described in the U.S. Pat. No. 6,092,610 issued to Alexandre G. E. Kosmala et al. on Jul. 25, 2000 and the U.S. Pat. App. No. 2002/0175003 published on Nov. 28, 2002 by Attilio C. Pisoni et al.
A point-the-bit system usually comprises of at least one bit shaft within the drilling collar. The bit shaft can be supported by a universal joint within the drilling collar and is rotatably driven by the drilling collar. For directional drilling purpose, the bit shaft must be maintained geostationary and axially inclined to the drilling collar during the drilling collar rotation. The point-the-bit system usually also incorporates a directional control method that the drill bit can be offset in the desired direction as the drilling tool rotates. However, the point-the-bit system requires complicated mechanical designs.
Therefore, a need exists for a rotary steerable drilling tool with simpler structure design.
A further need exists for a rotary steerable drilling tool with electromagnetic steering system to control the drilling direction.
The present embodiments of the present invention meet these needs and improve on the technology.
The present embodiments are detailed below with reference to the listed Figures.